In a textile fiber preparation installation, textile fibers which are pressed into bales and delivered in this form are opened up into small tufts, mixed and, if required, cleaned.
Metal parts, e.g. of harvesting and processing machines, are occasionally encountered in the textile bales. These metal parts can cause mechanical damage or fires in the preparation installation. In the textile industry, these metal parts have for about the last twenty years been detected and removed by means of induction coils. It has hitherto not been possible to detect non-ferrous extraneous components such as stones, aluminum, plastics and glass.
So-called extraneous fiber represent a further major problem for spinning works. These include pieces of fabric or tapes of other fiber in the bale. Pieces of jute or polypropylene sack wrapping are, for example, found in the bales. Other items include headscarves in cotton bales or cotton strings in cotton bales. Cotton strings or jute fiber in cotton fiber give rise to numerous thread breaks on the processing machines or may even damage the latter.
It is possible for a piece of polypropylene wrapping material in a cotton mixture to proceed unnoticed through the further processing stages. Only when the finished article of clothing is being dyed or pressed does the polypropylene fibre melt, ruining the articles of clothing. This occurence can lead to a high level of complaints.
The problems associated with extraneous fibers have risen steeply with the increase in automatic bale preparation since the beginning of the Sixties. To date, there is not a single device capable of removing such extraneous fibers on the market.